This invention relates to carbonate polymer compositions containing additives which act as thermal stabilizers.
Carbonate polymers derived from reactions of dihydroxyorganic compounds, particularly the dihydric phenols, and carbonic acid derivatives such as phosgene, have found extensive commercial application because of their excellent physical properties. These thermoplastic polymers are suitable for the manufacture of molded parts wherein impact strength, rigidity, toughness, heat resistance and excellent electrical properties are required.
In attempts to increase the desirable properties of carbonate polymers, it is common practice to incorporate therein numerous stabilizers. For example, organo-phosphite and organo-phosphonite compounds are useful as molecular weight stabilizers. As described in U.S. Pat. No. 4,360,617; hindered phenolic compounds can be employed with organo-phosphorus compounds in an attempt to enhance both the molecular weight stability and color stability of carbonate polymers. Unfortunately, the color stability of such compositions is not as great as would be desirable, especially when the carbonate polymer is subjected to warm and moist conditions.
The use of epoxide compounds in retarding the formation of haze and brittleness in carbonate polymers which are exposed to steam is disclosed in U.S. Pat. No. 3,839,247. Unfortunately, such compositions exhibit undesirable color stability as is evidenced by yellowness of the carbonate polymer composition.
In view of the deficiencies of the prior art, it would be highly desirable to provide a carbonate polymer composition which will exhibit good optical properties, improved optical stability at high temperatures, and improved retention of properties under hot and humid environments.